The present invention relates to a dual temperature refrigerated display case including a medium temperature open display case on top and a low temperature freezer open merchandizer on the bottom.
Dual temperature refrigerated display cases of this type have generally included separate air circulation systems providing cooled air to the display area of the medium temperature case on top and to the display area of the low temperature case on the bottom to maintain the products within each respective product display area at its desired temperature. The medium temperature case includes a fan and a medium temperature coil disposed in the base of the medium temperature case below the product display area. The fan draws air into an inlet at the front of the medium temperature case and then moves this air through the medium temperature coil. After passing through the coil, the air moves upwardly through a rear passageway behind the product display area, forwardly through an upper passageway above the product display area in the canopy, and downwardly out of a discharge outlet generating an air curtain across the front access opening of the product display area. Most of the air that defines the medium temperature air curtain is returned through the inlet to recirculate through the coil.
The low temperature case includes a fan and a low temperature coil disposed in the base of the low temperature case below the product display area. The fan draws air into an inlet at the front of the low temperature case and then moves this air through the low temperature coil. After passing through the coil, the air moves upwardly through a rear passageway behind the product display area, forwardly through an upper passageway above the product display area, and out of a discharge outlet at an angle generating an air curtain across an access opening of the product display area. Most of the air that defines the low temperature air curtain is returned through the inlet to recirculate through the coil.
Although stacking two different temperature cases in this manner provides advantages to marketing of product in a retail setting, it has provided challenges to maintaining case performance. For example, spillover air from the medium temperature air curtain (i.e., air which does not return to the medium temperature coil through the inlet) can dump into the low temperature case below thereby disrupting the low temperature air curtain allowing the intrusion of relatively humid, higher temperature air into the low temperature case causing potential issues in temperature performance within the low temperature case and frost formation on the low temperature coil. In the past, frost formation has been addressed through the addition of heaters on the low temperature coil. However, heaters, like other such energy producing components, add to the energy production of the case thereby decreasing case efficiency.